SERPINE1 and obesity due to melanocortin 4 receptor deficiency: To examine the synergistic effect of low PAI-1 and obesity on intraoperative bleeding volume, we categorized the parent population into four groups (group 1, low BMI and low PAI-1; group 2, high PAI-1 and low BMI; group 3, high PAI-1 and high BMI; group 4, low PAI-1 and high BMI) (Fig 2A).